[PATCH 01/23] dma-mapping: provide a generic DMA_MAPPING_ERROR

[Christoph Hellwig]

On Tue, Dec 04, 2018 at 04:41:34PM +0000, Robin Murphy wrote:
> I'd have been inclined to put the default check here, i.e.
>
> -	return 0
> +	return dma_addr == DMA_MAPPING_ERROR
>
> such that the callback retains full precedence and we don't have to deal 
> with the non-trivial removals immediately if it comes to it. Not that it 
> makes a vast difference though, so either way,

Ok, I've switched it around.